The FBI is planning to use digital billboards in 20 major cities to display each area's most-wanted fugitives, missing people, and high-priority security messages.

The nation's top cop is launching the project through a partnership with Clear Channel Outdoor, an advertising company that's providing the space as a public service, according to an FBI statement released Wednesday. The initiative follows a successful test of a billboard in Philadelphia.

The billboards, which will be placed near high-traffic areas, would enable the bureau to highlight the people it's looking for the most in a given area, whether they're violent criminals, kidnap victims, missing children, or terrorists. Pictures of victims or suspected criminals could be posted shortly after a crime is committed or a child is taken.

The FBI launched the Philadelphia test Sept. 13, displaying "crystal-clear images" of 11 of the city's most violent fugitives on eight billboards and a 24-hour hotline for people to call. In October, two fugitives were captured as a direct result of the publicity.

The billboards later helped catch a suspect in the Oct. 31 killing of Philadelphia police officer Charles Cassidy, who was slain during an armed robbery. The suspect was captured in Florida.